Light unit having light emitting diodes

ABSTRACT

A light unit is provided that includes a thin flexible substrate layer. A number of flexible electrical tracks are formed on the flexible substrate layer. A number of Light Emitting Diodes (LEDs) are arranged on the flexible substrate layer along the electrical tracks and are electrically connected to the electrical tracks such that the light unit is both thin and flexible.

BACKGROUND

[0001] The invention relates to a light unit. More particularly, thepresent invention relates to a light unit that includes Light EmittingDiodes (LEDs) and that is both thin and flexible.

[0002] Current incandescent lamps typically require too much room,especially when used in a closed room with restricted outer dimensions,such as in a motor vehicle (e.g., a passenger car).

[0003] Typically, an incandescent lamp has a depth of 70 mm to 150 mm,and hence separate tail lamp pockets need to be provided in and sealedagainst the quarter panels of the cars in order to accommodate theincandescent lamp. Such tail lamp pockets take up luggage space from theboot of the cars. Moreover, incandescent lamps require parabolicreflectors for light concentration and hence are limited to simplecircular or rectangular shapes, making it difficult to match theexternal contour of the body of the car. Incandescent lamps are alsoeasy to be damaged, and hence require to be replaced frequently.

[0004] Therefore, a much thinner and flexible light unit for lamps isdesirable.

SUMMARY OF THE INVENTION

[0005] One feature of the present invention is to provide a light unitthat is thin and flexible.

[0006] Another feature of the present invention is to provide a lightunit having LEDs as light source.

[0007] In accordance with one embodiment of the present invention, alight unit is provided that includes a thin flexible substrate layer. Anumber of flexible electrical tracks are formed on the flexiblesubstrate layer. A number of Light Emitting Diodes (LEDs) are arrangedon the flexible substrate layer along the electrical tracks and areelectrically connected to the electrical tracks such that the light unitis both thin and flexible.

[0008] In accordance with another embodiment of the present invention, amotor vehicle lamp is provided that includes a light unit that includesa flexible substrate layer. A number of flexible electrical tracks areformed on the flexible substrate layer. LEDs are arranged on theflexible substrate layer along the electrical tracks and areelectrically connected to the electrical tracks such that the light unitis both thin and flexible.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 shows a perspective view of a light unit according to oneembodiment of the invention.

[0010]FIG. 2 shows a side cross-sectional view of the light unit asshown in FIG. 1.

[0011]FIG. 3 shows an exploded view of the light unit of FIGS. 1-2.

[0012]FIG. 4 is a plan view of a partial circuit layout on the flexiblesubstrate of the light unit of FIGS. 1-3, showing a heat sink tracklayer arranged between an anode track layer and a cathode track layer.

[0013]FIG. 5 is a cross-sectional view of a portion of the light unit ofFIGS. 1-3, showing in a LED mounted on the tracks (both electrical andheat sink tracks) on the flexible substrate that is attached to themetal plate via an adhesive tape or paste.

[0014]FIG. 6 shows a front view of a motor vehicle lamp that includesthe light unit as shown in FIGS. 1-5.

[0015]FIG. 7 shows a top view of the motor vehicle lamp of FIG. 6.

[0016]FIG. 8 shows a schematic layout of electrical and heat sink tracksto be used in a light unit for the motor vehicle lamp of FIG. 6.

[0017]FIG. 9 shows a schematic circuit layout of the LEDs in the lightunit of FIGS. 6-8.

DETAILED DESCRIPTION

[0018]FIG. 1 shows a light unit 100 that implements one embodiment ofthe present invention. In accordance with one embodiment of the presentinvention, the light unit 100 may include a number of Light EmittingDiodes (e.g., LEDs 102 through 102 n) arranged on a thin and flexiblesubstrate (i.e., the substrate 103). The light unit 100 is thin andflexible, which in turn allows the light unit 100 to have a wide varietyof applications.

[0019] In one embodiment, the light unit 100 can be employed to build amotor vehicle lamp (see FIGS. 6-9). In a further embodiment, the lightunit 100 can be employed in other applications in which light source isneeded (e.g., lamps in rooms of buildings or working lamps to be carriedby hand).

[0020] As will be described in more detail below, the light unit 100includes a thin and flexible substrate layer 103. A number of flexibletracks (e.g., the tracks 121-126 in FIG. 4) are formed on the flexiblesubstrate layer 103. The tracks 121-126 include electrical tracks (e.g.,the tracks 121, 123-124, and 126) and heat sink tracks (e.g., the tracks122 and 125). The tracks may be arranged in a predetermined pattern onthe substrate layer 103 in accordance with a desired light form andintensity.

[0021] The LEDs (e.g., LEDs 102-102 n) are small surface mountable LEDsand may include heat sink. The LEDs are arranged (e.g., attached usingthe Surface Mounting Technology) on the flexible substrate 103 along thetracks (e.g., the tracks 121-126) and are electrically connected to theelectrical tracks (e.g., the tracks 121, 123-124, and 126) such that thelight unit 100 is both thin and flexible. This thin light unit 100 canbe used to make a vehicle lamp without the corresponding lamp pocket,which were otherwise necessary for incandescent lamps were not necessaryanymore. For example, a vehicle lamp with the light unit 100 inaccordance with one embodiment of the present invention can be made witha thickness of, for example, less than 10 mm. In one embodiment, thelight unit 100 has a thickness of less than 8 mm.

[0022] In addition, the light unit 100 may also include a heat sinkmetal frame (i.e., metal frame 108) on the substrate 103. The light unit100 may also include a metal plate (e.g., the metal plate 105) that mayserve both as heat sink and base support for the substrate 103. Anoptical lens (e.g., the lens 101) may be employed for the light unit100.

[0023] In addition, as the whole light unit 100 is flexible, it can bebent to a desired shape or contour, i.e. it can be easily formed tofollow the contour of a transparent part of a corresponding lamp. Thelight unit 100 in accordance with one embodiment of the presentinvention will be described in more detail below, also in conjunctionwith FIGS. 1-9.

[0024] Referring to FIGS. 1-5, the light unit 100 is shown to have thelens 101, the LEDs 102-102 n, the flexible substrate 103, a thermalconductive tape 104, and the heat sink plate 105. The tracks 121-126(see FIG. 4) are arranged on the substrate 103 and the substrate 103 isattached to the heat sink plate 105 via the tape 104. FIG. 2 also showsan air gap 110 between the LEDs 102-102 n and the lens 101. FIG. 3 showsthe exploded view of the light unit 100 (without showing the tracks onthe substrate 103). FIG. 4 shows the partial and illustrative layout ofthe tracks (i.e., the tracks 121-126) for illustration purposes. FIG. 5shows how each of the LEDs 102-102 n is mounted on the tracks (e.g., thetracks 121-126 of FIG. 4) on the flexible substrate 103 that is attachedto the metal plate 105 via the adhesive tape 104.

[0025] As described above, the flexible substrate 103 is a thin andflexible substrate. This means that the substrate 103 can be made of afilm or foil material, and can be easily bent by hand. The substrate 103may be made of an electrically insulating material. According to oneembodiment, the flexible substrate 103 is made of a synthetic material(e.g., polyamide). A substrate made of the above-mentioned polyamide canprovide for a sufficient electrical insulation as well as for asufficient flexibility and strength.

[0026] In one embodiment, the flexible substrate 103 is a flexibleprinted circuit board. In another embodiment, the flexible substrate 103has a thickness of about 25.4 micrometers. Alternatively, the substrate103 may have other thickness.

[0027] The tracks 121-126 (see FIG. 4) include electrical tracks (e.g.,the tracks 121, 123-124, and 126) and heat sink tracks (e.g., the tracks122 and 125). Each of the electrical tracks is of a conductive material(e.g., metal). The tracks may be arranged in a predetermined pattern onthe substrate layer 103 in accordance with a desired light form andintensity.

[0028] The electrical tracks (e.g., the tracks 121, 123-124, and 126)include at least an anode track or trace (e.g., the track 121 or 124)and a cathode track or trace (e.g., the track 123 or 126) extendingparallel to each other. An anode terminal and a cathode terminal of acorresponding LED are attached to the corresponding tracks. Therefore,various light patterns having light spots and dark zones can be formedin accordance with the form of a light or lamp to be created. FIG. 8shows, as an example, a schematic layout of electrical and heat sinktracks to be used in a light unit for the motor vehicle lamp 300 shownin FIGS. 6-7, which will be described in more detail below.

[0029] In one embodiment, each of the tracks 121-126 is formed of asingle material, such as a special metal. In another embodiment, each ofthe tracks 121-126 is formed of a multi-layer metal structure (notshown). In this embodiment, the track structure may include a copperlayer, a nickel layer on top of the copper layer, and a gold layer ontop of the nickel layer. Alternatively, some of the tracks may have themulti-layer structure while others may have a single metal layer.

[0030] In the multi-layer structure, the copper layer provides a goodmaterial for forming the circuit shape, the nickel layer helpspreventing copper migration and provides additional strength, and thegold layer is preferable in wire bonding and both electrical and heatconduction and thereby is very suitable for having the LED's attachedthereto. According to one embodiment, the copper layer is approximately17.78 micro-meter thick, the nickel layer is between 2.54 to 7.62micro-meter in thickness and the gold layer is at least 0.76 micro-meterin thickness. The relatively thick copper layer provides for asufficient cross-section for corresponding electrical energy supply, thenickel layer is kept relatively thinner in comparison to the copperlayer. The gold layer is also kept thinner than the nickel layer inorder to save costs.

[0031] The heat sink tracks or traces 122 and 125 are between theelectrical tracks such that they are parallel to the corresponding anodeand cathode tracks. In addition and as can be seen from FIG. 4, thelight unit 100 further includes an additional heat sink in a form of ametal frame 108 arranged on the substrate layer 103. The metal frame 108is in contact with the heat sink tracks 122 and 125 and is continuouslyextending around the substrate layer 103. With the metal frame 108, theheat from the LEDs 102-102 n is transported to the metal frame 108 viathe corresponding heat sink tracks.

[0032] As can be seen from FIGS. 1-3, the substrate 103 is attached to aheat sink metal plate 105 via a thermally conductive tape 104. The tape104 can be glue or paste. The metal plate 105 is also in contact withthe heat sink tracks (e.g., the tracks 122 and 124 in FIG. 4) on thesubstrate 103 and the frame 108. The heat sink metal plate 105 can bevery thin so that it can be easily bent to follow any required contourtogether with the flexible substrate 103. In addition, the metal plate105 also serves as a base support for the flexible substrate 103 withthe LEDs 102-102 n mounted thereon.

[0033] Each of the LEDs 102-102 n can be a high power surface mountableLED. In one embodiment, each of the LEDs is a High Flux SMT LEDmanufactured by Agilent Technologies, Inc. of Palo Alto, Calif.Alternatively, other types of LEDs can be used.

[0034] The LEDs 102-102 n are mounted on and along the respectiveelectrical tracks (e.g., the tracks 121, 123-124, and 126). Each of theLEDs 102-102 n is mounted in such a way that an anode terminal (notshown) of the LED is electrically connected to its corresponding anodetrack on the substrate 103, such as by soldering using screeningtechnique or gluing, and a cathode terminal (not shown) of the LED iselectrically connected to the corresponding cathode track on thesubstrate 103.

[0035] In one embodiment, each of the LEDs 102-102 n is attached to thecorresponding electrical tracks using the Surface Mounting Technology(SMT). This makes the light unit 100 anSMT-LED-package-on-flexible-substrate assembly.

[0036]FIG. 5 shows a cross-sectional view of a portion of the light unit100, showing how each of the LEDs 102-102 n is mounted on the tracks(e.g., the tracks 121-126 of FIG. 4) on the flexible substrate 103 thatis attached to the metal plate 105 via the adhesive tape 104. As can beseen from FIG. 5, solder paste is deposited on the exact locations ofthe anode and cathode tracks 131-132 using, for example, screeningtechniques. Thermally conductive glue is also applied to the heat sinktrack 133 using, for example, dispensing technique. The LED 102 i isthen placed onto the respective electrical tracks 131-132, with theanode and cathode terminals of the LED 102 i corresponding to the solderpaste deposited on the anode and cathode tracks 131-132. The LED 102 iis so placed such that its heat sink is in contact with the thermallyconductive glue deposited on the heat sink track 133. The LED 102 i issubsequently secured on the tracks 131-133 by reflow soldering of thesolder paste and curing the thermally conductive glue, respectively.

[0037] Referring back to FIGS. 1-3, the optical lens 101 is provided tocontrol, for example, the focusing or spreading of light emitted by theLEDs 102-102 n. The lens 101 is arranged slightly above the LEDs 102-102n with air gap 110 between the lens 110 and the LEDs 102-102 n.

[0038] The lens 101 may not be present in the light unit 101, or may bereplaced with something else. In one embodiment, the lens 101 may bereplaced with a transparent (or colored) cover. In another embodiment,the lens 101 may be replaced with other types of cover. Yet in otherembodiments, the light unit 100 may simply not include the lens 101. Inthis case, the LEDs may be encapsulated with, for example, transparentepoxy and there is no air gap 110.

[0039] In one embodiment, the thickness of the metal plate 105 is about0.64 mm (millimeter), the thickness of the substrate 103 is about 0.15mm, the thickness of each of the LEDs 102-102 n is about 2.20 mm and thethickness of the optical lens 110 is about 2.55 mm. This means that theassembled light unit 100 has a thickness of about 7.0 mm.

[0040] This thin and flexible light unit 100 eliminates the necessity ofhaving a space-wasting tail lamp pocket for a motor vehicle. Any motorvehicle lamp that employs the light unit 100 as the light source doesnot need a deep lamp pocket, since the light unit 100 is substantiallyflat in comparison with an incandescent lamp while still providing forsufficient light. Because of its flexibility, the light unit can beattached to a transparent part of the lamp, flexibly following thecontour of this transparent part.

[0041]FIGS. 6-9 show a motor vehicle lamp 300 that employs a light unitmade in accordance with one embodiment of the present invention, asdescribed above in connection with FIGS. 1-5. FIG. 6 shows a front viewof the motor vehicle lamp 300. FIG. 7 shows a top view of the motorvehicle lamp 300. FIG. 8 shows a schematic layout of electrical and heatsink tracks to be used in the light unit for the motor vehicle lamp 300and FIG. 9 shows a schematic circuit layout of the LEDs in the lightunit of the lamp 300.

[0042] As can be seen from FIGS. 6-7, the lamp 300 includes a lens 310and a light unit 320. An air gap 330 is between the lens 310 and thelight unit 320. It can be seen from FIGS. 6-7 that the lamp 300 thatimplements one embodiment of the invention is very thin, and is flexibleenough to be bent to follow the contour of the lamp 300.

[0043] Referring to FIG. 8, the electrical and heat sink tracks 340 ofthe light unit 320 are shown. As can be seen from FIG. 8, three clusterof LED positions 341-343, onto which LED's are to be mounted, are usedfor three different indication of the car. The first cluster 341includes twelve LED positions arranged in three rows, each rowcomprising four LED positions. A second cluster 342 is arranged to theright side of the first cluster 341. The second cluster 342 includeseighteen LED positions arranged in three rows, each row comprising sixLED positions. A third cluster 343 is arranged directly below the secondcluster 342. The third cluster 343 includes thirty-six LED positionsarranged in three rows, each row comprising twelve LED positions.

[0044] The electrical energy to the first cluster 341 is controlled by afirst anode track 345, indicating a “Reverse” light. The electricalenergy to the second cluster 342 is controlled by a second anode track346, indicating a “Signal” light. The electrical energy to the thirdcluster 343 is controlled by a third anode track 347, indicating a“Brake” light. All the clusters have a common cathode track 348. FIG. 9show a schematic circuit layout of the LEDs on the circuit layout 340 ofFIG. 8.

[0045] The present invention is not limited to the above-mentioned modesfor carrying out the present invention, and it is understood thatvarious configurations can be obtained in a range that does not departfrom the purport of the present invention.

1. (Canceled).
 2. (Canceled).
 3. A light unit comprising: a thin andflexible substrate layer; a plurality of flexible tracks, including atleast a heat sink track, formed on the flexible substrate, wherein theflexible tracks further comprise an anode track and a cathode track, andwherein the heat sink track is formed between the anode and cathodetracks; a plurality of Light Emitting Diodes (LEDs) arranged on theflexible substrate layer along the flexible tracks and beingelectrically connected to some of the flexible tracks such that thelight unit is both thin and flexible.
 4. A light unit comprising: a thinand flexible substrate layer; a plurality of flexible tracks, includingat least a heat sink track, formed on the flexible substrate; aplurality of Light Emitting Diodes (LEDs) arranged on the flexiblesubstrate layer along the flexible tracks and being electricallyconnected to some of the flexible tracks such that the light unit isboth thin and flexible; a heat-conducting frame surrounding thesubstrate layer, the heat sink track being thermally connected to theframe.
 5. The light unit of claim 4, further comprising a heatconducting metal plate attached with the substrate layer via an adhesivepaste and in contact with the heat-conducting frame.
 6. The light unitof claim 3, wherein the flexible substrate layer comprises anelectrically insulating material and is about 25.4 micrometer inthickness.
 7. Light unit of claim 3, wherein the flexible tracks aremulti-layer tracks that comprise a copper layer on the substrate layer,a nickel layer arranged over the copper layer, and a gold layer over thenickel layer.
 8. The light unit of claim 7, wherein the copper layer isabout 17.78 micro-meter thick, the nickel layer is between 2.54 to 7.62micro-meter in thickness and the gold layer is at least 0.76 micro-meterin thickness.
 9. The light unit of claim 3, wherein each of the LEDs isarranged on the substrate layer along the flexible tracks using asurface mount technology.
 10. (Canceled).
 11. (Canceled).
 12. A motorvehicle lamp comprising: a light unit that further comprises a thinflexible substrate layer; a plurality of flexible tracks, including atleast a heat sink track, formed on the flexible substrate, wherein theflexible tracks further comprise an anode track and a cathode track, andwherein the heat sink track is formed between the anode and cathodetracks; a plurality of Light Emitting Diodes (LEDs) arranged on thesubstrate layer along the flexible tracks and being electricallyconnected to some of the flexible tracks such that the light unit isboth thin and flexible.
 13. A motor vehicle lamp comprising: a lightunit that further comprises a thin flexible substrate layer; a pluralityof flexible tracks, including at least a heat sink track, formed on theflexible substrate; a plurality of Light Emitting Diodes (LEDs) arrangedon the substrate layer along the flexible tracks and being electricallyconnected to some of the flexible tracks such that the light unit isboth thin and flexible; and a heat-conducting frame surrounding thesubstrate layer, the heat sink track being thermally connected to theframe.
 14. The motor vehicle lamp of claim 13, wherein the light unitfurther comprises a heat conducting metal plate attached with thesubstrate layer via an adhesive paste and in contact with theheat-conducting frame.
 15. The motor vehicle lamp of claim 12, whereinthe flexible substrate layer comprises an electrically insulatingmaterial and is about 25.4 micrometer in thickness.
 16. The motorvehicle lamp of claim 12, wherein the flexible tracks are multi-layertracks that comprise a copper layer on the substrate layer, a nickellayer arranged over the copper layer, and a gold layer over the nickellayer.
 17. The motor vehicle lamp of claim 16, wherein the copper layeris approximately 17.78 micro-meter thick, the nickel layer is between2.54 to 7.62 micro-meter in thickness and the gold layer is at least0.76 micro-meter in thickness.
 18. The motor vehicle lamp of claim 12,wherein the lamp is a tail lamp.
 19. The motor vehicle lamp of claim 12,further comprising a casing within which the light unit is arranged withthe transparent part being provided as a cover covering the casing. 20.The motor vehicle lamp of claim 12, wherein the light unit furthercomprises an optical lens arranged on the LEDs for controlling lightemitted thereby, wherein each of the LEDs is arranged on the substratelayer along the flexible tracks using a surface mount technology. 21.The light unit of claim 4, wherein the flexible substrate layercomprises an electrically insulating material and is about 25.4micrometer in thickness.
 22. The motor vehicle lamp of claim 13, whereinthe flexible substrate layer comprises an electrically insulatingmaterial and is about 25.4 micrometer in thickness.
 23. The motorvehicle lamp of claim 13, wherein the lamp is a tail lamp.
 24. The motorvehicle lamp of claim 13, further comprising a casing within which thelight unit is arranged with the transparent part being provided as acover covering the casing.
 25. The motor vehicle lamp of claim 13,wherein the light unit further comprises an optical lens arranged on theLEDs for controlling light emitted thereby, wherein each of the LEDs isarranged on the substrate layer along the flexible tracks using asurface mount technology.